1. Field of the Invention
This invention relates in general to earth boring drill bits, and in particular to a cutter mounting for a large hole earth boring drill bit.
2. Description of the Prior Art
One phase of the earth boring industry is concerned with drilling large diameter holes for mining. Normally several cutters are mounted on frames which are mounted to a large cutter support plate. The cutter support plate is connected to a drill string and rotated with each cutter rotating on its individual frame. Drilling is performed by pulling upward through a small diameter pilot hole, or by blind shaft drilling without using the pilot hole.
The cutters are carried by bearings and mounted to individual frames that are welded to the cutter support plate. Various devices including pins and bolts are used to mount the bearing carrier to the frame. Bolts require high torques and still occasionally become unscrewed because of the high vibratory forces. If a pin is used in a clevis-type arrangement, the two holes of the frame must be aligned with the hole in the bearing carrier within very small tolerances to minimize any play between them. This type of clevis is expensive to construct and a certain amount of play always remains.